Through the research and training described in this K01 proposal, the PI (Dr. Aston) will acquire the necessary skills to become an independent researcher applying a behavioral economic framework to the examination of the relative value, behavioral, and pharmacologic effects of marijuana. Behavioral economics incorporates principles from economics and psychology to examine decision-making, the degree to which a user values a given substance, and consumption behavior. Substance demand refers to the effects of drug cost on willingness to purchase drugs for consumption. Current and impending legalization of marijuana for recreational purposes makes the examination of behavioral economic demand for marijuana timely and of high priority. Via use of drug purchase tasks, behavioral economics has been used extensively in the literature to assess the relative value of both alcohol and nicotine under various conditions and as a predictor of future behavior. However, there is a paucity of research on the relative value of marijuana. The aim of this proposal is to develop, refine, and validate a Marijuana Purchase Task (MPT) to assess marijuana demand. This is the first proposal to qualitatively develop an MPT measure, and as such, will contribute to the understanding of the relationships among marijuana demand, use, and purchase behavior. A mixed-methods approach will be employed across two aims. First, a qualitative approach (focus groups with 30-48 frequent marijuana users; cognitive interviews with 20-30 users) will be used to develop and refine an MPT measure and to contribute to the limited literature on marijuana use and purchase. Subsequently, frequent marijuana users (n=85) will be recruited to participate in two counter-balanced marijuana administration sessions (marijuana cue-reactivity and smoking topography) to validate the MPT measure. The PI will work with an experienced and knowledgeable team of mentors (Drs. Jane Metrik, James MacKillop, Robert Swift, and Rochelle Rosen) to master five areas of training relevant to this proposal: (1) qualitative methodology and analysis, (2) pharmacotherapy for substance use disorders, (3) laboratory marijuana administration methodology, (4) behavioral economic theory and analysis, and (5) advanced statistical approaches to data analysis. Successful completion of the research and training detailed in this application will prepare the PI to become an independent scientist and develop lines of research on the behavioral economic and pharmacologic effects of substance use. This proposal will result in a valid and reliable measure of demand for marijuana. Successful development of a measure of marijuana demand will significantly impact the field via facilitation of subsequent research examining (1) potential mediators and moderators between marijuana demand and use, (2) demand for synthetic versus plant-based cannabinoids, (3) potential pharmacotherapy for cannabis use disorders, (4) the influence of taxation on demand for recreational and black-market marijuana, and (5) variation in demand, pharmacologic effects, and behavioral effects of co-administration of alcohol and marijuana.